Surge protection devices for industrial applications

Surge protection devices for industrial applications

Industrial applications include various types of equipment that need to be protected from the effects of surges. They are costly to the company owner: the price may be enormous and the failure, or even replacement, of those devices, would incur a major financial loss, possibly putting the very existence of the company at stake. The key aspects, from the perspective of trade unions, are the employees: they operate electrical equipment and, in the event of a surge, their lives might be at risk. The facts mentioned above, as well as other causes, represent substantial reasons why one should seek protection from surges. This function uses internal and external protection from lightning, such as the air terminals, grounding, protective busbar, surge suppressors, all jointly referred to as surge protection devices, SPD. There are a number of companies that produce a plethora of devices, yet not all of them are suitable for industrial applications.

External Lightning Protection of an Industrial Building

Internal lightning protection and surge protection for the industrial building

The heart of it all, as the case typically is, lies in a directive or a legal requirement. In this specific situation, it is standard EN 62305 Lightning Protection, Parts I through 4. The text also defines individual types of loss, risk, lightning protection systems as well as the level of lightning protection. There are four levels of lightning protection (I through IV) which specify the parameters of lightning; the protection levels are the function of the risk level. In most industrial applications, the building is classified as Level I or II. This corresponds to the peak values of lightning current Iimp (the current impulse with parameters 10/350 µs) being as high as 200 kA. A qualified estimate suggests that 50 % of the overall Iimp current is arrested by the air terminals and delivered into the grounding system. The remaining 50 % becomes equally distributed among the inputs (i.e. among the external contacts entering the building), typically to the IT and communication cables, metal piping and LV power supply cables.

In the most adverse of situations, SPD needs to arrest as much as 100 kA. When distributed into individual strands, the current values amount to 25 kA per strand (using a TN-C) system. That is why we recommend that master distributors of LV unit substations (in buildings qualifying as LPL I protection level) be fitted with the FLP50GR sealed spark gap with gas filling. Being SPD Type 1, the equipment guarantees the equalization of potential and disposal of the lightning current as well as the switching surge that is generated in the power supply lines entering the building.

It is capable of arresting Iimp currents as large as 50 kA. Unit substations of individual buildings then should be fitted with the FLP25GR, a combination of SPD Type 1 and 2, that features dual varistors for higher safety and offers 25 kA of arrestable impulse current. Secondary substations and control cabinets should be equipped with SPD Type 2. An example of that class in our product range is the SLP40, which is offered as a complete, sealed unit or with replaceable modules.

If the protected device is located within 5 m from the secondary substation or control cabinet, the system must be further equipped with an SPD Type 3 unit, for example, the TLP10. It is a high-frequency filter with attenuation min. 30 dB in the frequency band 0.15 – 30 MHz that also features protective devices – varistors produced for rated currents from 16 to 400 A. In that case, an impulse separation suppressor LC63 needs to be inserted between SPD Type 2 and 3 to provide correct coordination of the arresters. Shielded cables need to be provided between the substation and the protected equipment for its proper operation.

LSP also offers protection for situations where the roof of the building bears photovoltaic panels. Our recommendation is the SLP40-PV series that mounts before the inverter and its interior is fitted with disconnectors which are deployed in the event of failure (overheating) of the varistors and with a mechanical stop, that is inserted between the disconnected electrodes to prepare ideal conditions to kill a DC arc. Surge protection for alternating current is necessary, the best choice is the FLP7-PV series.

We recommend that arresters of this type be installed in rooms such as server halls, control rooms, and offices. Tele-Defender-RJ11-TELE for protection of telecommunication equipment, Net-Defender-RJ45-E100 for protection of transmission of data and information signals, COAX-BNC-FM for protection of equipment that processes transmitted video signal, Net-Defender-ND-CAT-6AEAare designed for computer networks prior to entering the network card and they are purpose designed for protection and data transmission in Generation 5 networks, and RJ45S-E100-24U for installation in 19-inch distributors at the server for protection of data transmission in computer networks: the device offers RJ45 sockets as well as LSA-PLUS connectors. For the protection of data and communication lines and for I&C instrumentation and controls for production lines, machinery, and critical equipment, we recommend using FLD2 series which deliver protection with lightning arresters and transient-voltage-suppression diodes. They are offered in various designs with a selectable number of pairs and rated operating voltage in a given series. For communications with the RS 485 serial interface, we offer protection of those lines using FLD2 series that protects the connected equipment against the transverse and longitudinal surge. Protection of cameras and video signal aggregators, especially in electronic security systems and electronic fire protection systems EPS uses the FLPD2 with non-linear components for currents Imax up to 6.5 kA. Protection of devices connected to the antenna system with coaxial cable should be fitted with surge protectors. LSP offers a wide range of coaxial protectors for various types of connectors and specific performance classes that can be used in many types of applications. This SPD contains special lightning arresters with the maximum discharge current of Imax (8/20 µs) = 10 kA to provide reliable protection of reception and broadcasting systems against the effects of a lightning strike in close vicinity. They offer high attenuation of recoil no less than 20 dB.

The topic of protection against surges is not an easy one; the proper design depends on a number of contributing factors. We are inviting you to please contact our qualified sales representatives who will be happy to advise you in selecting the proper type of surge protection to provide protection of your property and minimize the loss and damage of your property.

Requirements for use of Surge Protective Devices (SPDs) in Industrial Control Panels

Surge Protective Devices (SPDs) are commonly used in industrial control panels. The table below is an itemization of SPD types and how they can be used in panels where no Procedure description is required. The requirements for the Voltage and Nominal Discharge Current (NDC) ratings of the SPD are indicated in the table below. SPDs that are used outside the guidelines of this table requires Procedure description. Depending on the evaluation of the SPD, these guidelines can be exceeded if an engineering evaluation is conducted.

The table applies to “One-Port” SPDs, which are most common. Where a “Two-Port” SPD is used, it shall be a permitted type in the table above, based on the panel usage, and be used within its marked ratings, including the Short Circuit Current Rating (SCCR). When two-port Type 3 SPDs are not marked with an SCCR, it is assumed to be 1000A. If the Two-Port device is Recognized with a Note 4 in the Listing Information Page (indicating that external overcurrent protection is required), this SPD needs to be procedure described.

R/C denotes Recognized Component

1, Includes panels marked “Suitable for Use as Service Equipment”

2, The voltage rating of the SPD shall be at least that of the circuit’s full phase (L-L) voltage for all modes (i.e. L-N, L-L, L-G). For example, panels rated 277/480V shall use SPD rated 480V in all modes; panels rated 120 or 120/240 shall use SPD rated 240V in all modes.

SPD Terminology:

One Port – SPD is across-the-line.

Two Port – SPD is across-the-line, plus additional circuitry in series with a load. Current flow through this device shall not exceed its marked current rating.

Notes – Clarification of requirements:

Where rated Voltage is specified, MCOV (Maximum Continuous Operating Voltage) values may be

Nominal Discharge Current (NDC): May also be referred to as IN. The typical ratings are 3kA, 5kA, 10kA, or 20kA.Definitions – from UL1449 (informative)

Type Ratings (applicable to certifications before April 2010):

Type 1 – Permanently connected SPDs intended for installation between the secondary of the service transformer and the line side of the service equipment overcurrent device, as well as the load side, including watt-hour meter socket enclosures and intended to be installed without an external overcurrent protective device.

These devices are Listed.

Type 2 – Permanently connected SPDs intended for installation on the load side of the service equipment overcurrent device; including SPDs located at the branch panel.

These devices are Listed.

Type 3 – Point of utilization SPDs, installed at a minimum conductor length of 10 meters (30 feet) from the electrical service panel to the point of utilization, for example, cord connected, direct plug-in, receptacle type and SPDs installed at the utilization equipment being protected. See marking in 64.2. The distance (10 meters) is exclusive of conductors provided with or used to attach SPDs.

These devices are Listed.

Type 4 Component SPDs, including discrete components as well as component assemblies.

These devices are Recognized as “Type 4 for use in xxx applications” where xxx may be 1, 2, 3, or “other”. Type ratings (applicable to certifications after April 2010):

Type 1 – Permanently connected SPDs intended for installation between the secondary of the service transformer and the line side of the service equipment overcurrent device, as well as the load side, including watt-hour meter socket enclosures and intended to be installed without an external overcurrent protective device.

These devices are Listed.

Type 2 – Permanently connected SPDs intended for installation on the load side of the service equipment overcurrent device; including SPDs located at the branch panel.

These devices are Listed.

Type 3 – Point of utilization SPDs, installed at a minimum conductor length of 10 meters (30 feet) from the electrical service panel to the point of utilization, for example, cord connected, direct plug-in, receptacle type and SPDs installed at the utilization equipment being protected.

These are assemblies that are similar to UL508’s “Open Type Devices.” They may be DIN rail mounted for panel installation. Type 1 and 2 component assemblies have undergone short circuit testing.

Type 4 Component Assemblies – Component assembly consisting of one or more Type 5 components together with a disconnect (integral or external) or a means of complying with the limited current tests in UL1449 section 44.4 (4th edition). These devices are Recognized, typically discrete having some sort of thermal protection. They may or may not have undergone short circuit testing.

Type 5 – Discrete component surge suppressors, such as MOVs that may be mounted on a PWB, connected by its leads or provided within an enclosure with mounting means and wiring terminations.

These devices are Recognized, typically discrete having no thermal protection.